1 .. Copyright 2010 Nicolas Palix <npalix@diku.dk>
2 .. Copyright 2010 Julia Lawall <julia@diku.dk>
3 .. Copyright 2010 Gilles Muller <Gilles.Muller@lip6.fr>
10 Coccinelle is a tool for pattern matching and text transformation that has
11 many uses in kernel development, including the application of complex,
12 tree-wide patches and detection of problematic programming patterns.
17 The semantic patches included in the kernel use features and options
18 which are provided by Coccinelle version 1.0.0-rc11 and above.
19 Using earlier versions will fail as the option names used by
20 the Coccinelle files and coccicheck have been updated.
22 Coccinelle is available through the package manager
23 of many distributions, e.g. :
33 Some distribution packages are obsolete and it is recommended
34 to use the latest version released from the Coccinelle homepage at
35 http://coccinelle.lip6.fr/
39 https://github.com/coccinelle/coccinelle
41 Once you have it, run the following commands::
47 as a regular user, and install it with::
51 More detailed installation instructions to build from source can be
54 https://github.com/coccinelle/coccinelle/blob/master/install.txt
56 Supplemental documentation
57 ---------------------------
59 For supplemental documentation refer to the wiki:
61 https://bottest.wiki.kernel.org/coccicheck
63 The wiki documentation always refers to the linux-next version of the script.
65 For Semantic Patch Language(SmPL) grammar documentation refer to:
67 http://coccinelle.lip6.fr/documentation.php
69 Using Coccinelle on the Linux kernel
70 ------------------------------------
72 A Coccinelle-specific target is defined in the top level
73 Makefile. This target is named ``coccicheck`` and calls the ``coccicheck``
74 front-end in the ``scripts`` directory.
76 Four basic modes are defined: ``patch``, ``report``, ``context``, and
77 ``org``. The mode to use is specified by setting the MODE variable with
80 - ``patch`` proposes a fix, when possible.
82 - ``report`` generates a list in the following format:
83 file:line:column-column: message
85 - ``context`` highlights lines of interest and their context in a
86 diff-like style.Lines of interest are indicated with ``-``.
88 - ``org`` generates a report in the Org mode format of Emacs.
90 Note that not all semantic patches implement all modes. For easy use
91 of Coccinelle, the default mode is "report".
93 Two other modes provide some common combinations of these modes.
95 - ``chain`` tries the previous modes in the order above until one succeeds.
97 - ``rep+ctxt`` runs successively the report mode and the context mode.
98 It should be used with the C option (described later)
99 which checks the code on a file basis.
104 To make a report for every semantic patch, run the following command::
106 make coccicheck MODE=report
108 To produce patches, run::
110 make coccicheck MODE=patch
113 The coccicheck target applies every semantic patch available in the
114 sub-directories of ``scripts/coccinelle`` to the entire Linux kernel.
116 For each semantic patch, a commit message is proposed. It gives a
117 description of the problem being checked by the semantic patch, and
118 includes a reference to Coccinelle.
120 As any static code analyzer, Coccinelle produces false
121 positives. Thus, reports must be carefully checked, and patches
124 To enable verbose messages set the V= variable, for example::
126 make coccicheck MODE=report V=1
128 Coccinelle parallelization
129 ---------------------------
131 By default, coccicheck tries to run as parallel as possible. To change
132 the parallelism, set the J= variable. For example, to run across 4 CPUs::
134 make coccicheck MODE=report J=4
136 As of Coccinelle 1.0.2 Coccinelle uses Ocaml parmap for parallelization,
137 if support for this is detected you will benefit from parmap parallelization.
139 When parmap is enabled coccicheck will enable dynamic load balancing by using
140 ``--chunksize 1`` argument, this ensures we keep feeding threads with work
141 one by one, so that we avoid the situation where most work gets done by only
142 a few threads. With dynamic load balancing, if a thread finishes early we keep
143 feeding it more work.
145 When parmap is enabled, if an error occurs in Coccinelle, this error
146 value is propagated back, the return value of the ``make coccicheck``
147 captures this return value.
149 Using Coccinelle with a single semantic patch
150 ---------------------------------------------
152 The optional make variable COCCI can be used to check a single
153 semantic patch. In that case, the variable must be initialized with
154 the name of the semantic patch to apply.
158 make coccicheck COCCI=<my_SP.cocci> MODE=patch
162 make coccicheck COCCI=<my_SP.cocci> MODE=report
165 Controlling Which Files are Processed by Coccinelle
166 ---------------------------------------------------
168 By default the entire kernel source tree is checked.
170 To apply Coccinelle to a specific directory, ``M=`` can be used.
171 For example, to check drivers/net/wireless/ one may write::
173 make coccicheck M=drivers/net/wireless/
175 To apply Coccinelle on a file basis, instead of a directory basis, the
176 following command may be used::
178 make C=1 CHECK="scripts/coccicheck"
180 To check only newly edited code, use the value 2 for the C flag, i.e.::
182 make C=2 CHECK="scripts/coccicheck"
184 In these modes, which works on a file basis, there is no information
185 about semantic patches displayed, and no commit message proposed.
187 This runs every semantic patch in scripts/coccinelle by default. The
188 COCCI variable may additionally be used to only apply a single
189 semantic patch as shown in the previous section.
191 The "report" mode is the default. You can select another one with the
192 MODE variable explained above.
194 Debugging Coccinelle SmPL patches
195 ---------------------------------
197 Using coccicheck is best as it provides in the spatch command line
198 include options matching the options used when we compile the kernel.
199 You can learn what these options are by using V=1, you could then
200 manually run Coccinelle with debug options added.
202 Alternatively you can debug running Coccinelle against SmPL patches
203 by asking for stderr to be redirected to stderr, by default stderr
204 is redirected to /dev/null, if you'd like to capture stderr you
205 can specify the ``DEBUG_FILE="file.txt"`` option to coccicheck. For
209 make coccicheck COCCI=scripts/coccinelle/free/kfree.cocci MODE=report DEBUG_FILE=cocci.err
212 You can use SPFLAGS to add debugging flags, for instance you may want to
213 add both --profile --show-trying to SPFLAGS when debugging. For instance
214 you may want to use::
217 export COCCI=scripts/coccinelle/misc/irqf_oneshot.cocci
218 make coccicheck DEBUG_FILE="err.log" MODE=report SPFLAGS="--profile --show-trying" M=./drivers/mfd/arizona-irq.c
220 err.log will now have the profiling information, while stdout will
221 provide some progress information as Coccinelle moves forward with
224 DEBUG_FILE support is only supported when using coccinelle >= 1.0.2.
229 Coccinelle supports reading .cocciconfig for default Coccinelle options that
230 should be used every time spatch is spawned, the order of precedence for
231 variables for .cocciconfig is as follows:
233 - Your current user's home directory is processed first
234 - Your directory from which spatch is called is processed next
235 - The directory provided with the --dir option is processed last, if used
237 Since coccicheck runs through make, it naturally runs from the kernel
238 proper dir, as such the second rule above would be implied for picking up a
239 .cocciconfig when using ``make coccicheck``.
241 ``make coccicheck`` also supports using M= targets. If you do not supply
242 any M= target, it is assumed you want to target the entire kernel.
243 The kernel coccicheck script has::
245 if [ "$KBUILD_EXTMOD" = "" ] ; then
246 OPTIONS="--dir $srctree $COCCIINCLUDE"
248 OPTIONS="--dir $KBUILD_EXTMOD $COCCIINCLUDE"
251 KBUILD_EXTMOD is set when an explicit target with M= is used. For both cases
252 the spatch --dir argument is used, as such third rule applies when whether M=
253 is used or not, and when M= is used the target directory can have its own
254 .cocciconfig file. When M= is not passed as an argument to coccicheck the
255 target directory is the same as the directory from where spatch was called.
257 If not using the kernel's coccicheck target, keep the above precedence
258 order logic of .cocciconfig reading. If using the kernel's coccicheck target,
259 override any of the kernel's .coccicheck's settings using SPFLAGS.
261 We help Coccinelle when used against Linux with a set of sensible defaults
262 options for Linux with our own Linux .cocciconfig. This hints to coccinelle
263 git can be used for ``git grep`` queries over coccigrep. A timeout of 200
264 seconds should suffice for now.
266 The options picked up by coccinelle when reading a .cocciconfig do not appear
267 as arguments to spatch processes running on your system, to confirm what
268 options will be used by Coccinelle run::
270 spatch --print-options-only
272 You can override with your own preferred index option by using SPFLAGS. Take
273 note that when there are conflicting options Coccinelle takes precedence for
274 the last options passed. Using .cocciconfig is possible to use idutils, however
275 given the order of precedence followed by Coccinelle, since the kernel now
276 carries its own .cocciconfig, you will need to use SPFLAGS to use idutils if
277 desired. See below section "Additional flags" for more details on how to use
283 Additional flags can be passed to spatch through the SPFLAGS
284 variable. This works as Coccinelle respects the last flags
285 given to it when options are in conflict. ::
287 make SPFLAGS=--use-glimpse coccicheck
289 Coccinelle supports idutils as well but requires coccinelle >= 1.0.6.
290 When no ID file is specified coccinelle assumes your ID database file
291 is in the file .id-utils.index on the top level of the kernel, coccinelle
292 carries a script scripts/idutils_index.sh which creates the database with::
294 mkid -i C --output .id-utils.index
296 If you have another database filename you can also just symlink with this
299 make SPFLAGS=--use-idutils coccicheck
301 Alternatively you can specify the database filename explicitly, for
304 make SPFLAGS="--use-idutils /full-path/to/ID" coccicheck
306 See ``spatch --help`` to learn more about spatch options.
308 Note that the ``--use-glimpse`` and ``--use-idutils`` options
309 require external tools for indexing the code. None of them is
310 thus active by default. However, by indexing the code with
311 one of these tools, and according to the cocci file used,
312 spatch could proceed the entire code base more quickly.
314 SmPL patch specific options
315 ---------------------------
317 SmPL patches can have their own requirements for options passed
318 to Coccinelle. SmPL patch specific options can be provided by
319 providing them at the top of the SmPL patch, for instance::
321 // Options: --no-includes --include-headers
323 SmPL patch Coccinelle requirements
324 ----------------------------------
326 As Coccinelle features get added some more advanced SmPL patches
327 may require newer versions of Coccinelle. If an SmPL patch requires
328 at least a version of Coccinelle, this can be specified as follows,
329 as an example if requiring at least Coccinelle >= 1.0.5::
333 Proposing new semantic patches
334 -------------------------------
336 New semantic patches can be proposed and submitted by kernel
337 developers. For sake of clarity, they should be organized in the
338 sub-directories of ``scripts/coccinelle/``.
341 Detailed description of the ``report`` mode
342 -------------------------------------------
344 ``report`` generates a list in the following format::
346 file:line:column-column: message
353 make coccicheck MODE=report COCCI=scripts/coccinelle/api/err_cast.cocci
355 will execute the following part of the SmPL script::
358 @r depends on !context && !patch && (org || report)@
363 ERR_PTR@p(PTR_ERR(x))
365 @script:python depends on report@
370 msg="ERR_CAST can be used with %s" % (x)
371 coccilib.report.print_report(p[0], msg)
374 This SmPL excerpt generates entries on the standard output, as
377 /home/user/linux/crypto/ctr.c:188:9-16: ERR_CAST can be used with alg
378 /home/user/linux/crypto/authenc.c:619:9-16: ERR_CAST can be used with auth
379 /home/user/linux/crypto/xts.c:227:9-16: ERR_CAST can be used with alg
382 Detailed description of the ``patch`` mode
383 ------------------------------------------
385 When the ``patch`` mode is available, it proposes a fix for each problem
393 make coccicheck MODE=patch COCCI=scripts/coccinelle/api/err_cast.cocci
395 will execute the following part of the SmPL script::
398 @ depends on !context && patch && !org && !report @
402 - ERR_PTR(PTR_ERR(x))
406 This SmPL excerpt generates patch hunks on the standard output, as
409 diff -u -p a/crypto/ctr.c b/crypto/ctr.c
410 --- a/crypto/ctr.c 2010-05-26 10:49:38.000000000 +0200
411 +++ b/crypto/ctr.c 2010-06-03 23:44:49.000000000 +0200
412 @@ -185,7 +185,7 @@ static struct crypto_instance *crypto_ct
413 alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
414 CRYPTO_ALG_TYPE_MASK);
416 - return ERR_PTR(PTR_ERR(alg));
417 + return ERR_CAST(alg);
419 /* Block size must be >= 4 bytes. */
422 Detailed description of the ``context`` mode
423 --------------------------------------------
425 ``context`` highlights lines of interest and their context
426 in a diff-like style.
428 **NOTE**: The diff-like output generated is NOT an applicable patch. The
429 intent of the ``context`` mode is to highlight the important lines
430 (annotated with minus, ``-``) and gives some surrounding context
431 lines around. This output can be used with the diff mode of
432 Emacs to review the code.
439 make coccicheck MODE=context COCCI=scripts/coccinelle/api/err_cast.cocci
441 will execute the following part of the SmPL script::
444 @ depends on context && !patch && !org && !report@
448 * ERR_PTR(PTR_ERR(x))
451 This SmPL excerpt generates diff hunks on the standard output, as
454 diff -u -p /home/user/linux/crypto/ctr.c /tmp/nothing
455 --- /home/user/linux/crypto/ctr.c 2010-05-26 10:49:38.000000000 +0200
457 @@ -185,7 +185,6 @@ static struct crypto_instance *crypto_ct
458 alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
459 CRYPTO_ALG_TYPE_MASK);
461 - return ERR_PTR(PTR_ERR(alg));
463 /* Block size must be >= 4 bytes. */
466 Detailed description of the ``org`` mode
467 ----------------------------------------
469 ``org`` generates a report in the Org mode format of Emacs.
476 make coccicheck MODE=org COCCI=scripts/coccinelle/api/err_cast.cocci
478 will execute the following part of the SmPL script::
481 @r depends on !context && !patch && (org || report)@
486 ERR_PTR@p(PTR_ERR(x))
488 @script:python depends on org@
493 msg="ERR_CAST can be used with %s" % (x)
494 msg_safe=msg.replace("[","@(").replace("]",")")
495 coccilib.org.print_todo(p[0], msg_safe)
498 This SmPL excerpt generates Org entries on the standard output, as
501 * TODO [[view:/home/user/linux/crypto/ctr.c::face=ovl-face1::linb=188::colb=9::cole=16][ERR_CAST can be used with alg]]
502 * TODO [[view:/home/user/linux/crypto/authenc.c::face=ovl-face1::linb=619::colb=9::cole=16][ERR_CAST can be used with auth]]
503 * TODO [[view:/home/user/linux/crypto/xts.c::face=ovl-face1::linb=227::colb=9::cole=16][ERR_CAST can be used with alg]]